The speed of modern ink jet printers has to increase steadily for economic reasons. Particularly suitable recording sheets for such printers comprise nanoporous inorganic compounds such as for example silicium dioxide, aluminum oxide/hydroxide, aluminum oxide or their mixtures. Such recording sheets are known as “nanoporous recording sheets”. Images printed onto these recording sheets need to have a good storage stability even under adverse conditions. This can only be achieved by using a finely tuned system of inks, respectively the dyes contained therein.
Up to now, these images do not satisfy all required properties. In particular, the water fastness, the light stability, the ozone stability, the hue and the brilliance of images printed onto these recording sheets are not satisfactory. Thus, new dyes are looked for which would improve the properties mentioned above of images printed onto these recording sheets, in particular in areas with black hue.
In addition to this, industrial ink jet is getting more and more significant in the packaging and food packaging industry. In that segment waterfastness, lightfastness and the use of safe components is a must. It is also required that these properties are the same independently to the recording medium used.
Although quite a number black dyes have already been proposed as black dyes for ink jet printing. However, none satisfies all of the required properties.
In addition to this the dyes should present a good water solubility being human and ecologically safe.
The following black dyes are often used in industrial ink jet Printers:
C.I. Acid Black 1 with the Formula (I)

This dye is too bluish and present poor waterfastness when printed on standard plain paper.

The direct black 19 that present a good waterfastness is usually available as a mixture containing different side products and is described to be tested mutagenic (U.S. Pat. No. 5,340,929).
Although quite a number black dyes have already been proposed as black dyes for ink jet printing as in the U.S. Pat. No. 5,423,906 and US 2012/0090503 A1. However, none satisfies all of the required properties.
Various types of ink compositions have been proposed. Typical inks comprise one or more dyes or pigments, water, organic co-solvents and other additives.
The inks have to satisfy the following criteria:                (1) The ink gives images of excellent quality on any type of recording sheet.        (2) The ink gives printed images exhibiting good water fastness.        (3) The ink gives printed images exhibiting good light stability.        (4) The ink gives printed images exhibiting good ozone fastness.        (5) The ink gives printed images exhibiting excellent smudge behavior.        (6) The ink gives printed images exhibiting excellent storage stability under conditions of high temperature and humidity.        (7) The ink does not clog jetting nozzles of the ink jet printers even when these are kept uncapped while recording is suspended for long periods.        (8) The ink may be stored for long periods without deterioration of its quality.        (9) The ink has to be non-toxic, non-flammable and safe.        